This invention concerns an endoscope using a line transfer type solid state image sensing element suitable for miniaturization.
Recently, various kinds of endoscopes using solid state image sensing elements, such as charge coupled devices for the image sensing means, are being proposed.
The endoscopes using the aforementioned solid stage image sensing elements have the advantages that it is possible to prevent the quality of pictures from deteriorating due to the breaking of fibers in the endoscope using the image guide made of an optical fiber bundle and that it is easy to record pictures, and it is expected that they will be increasingly used in the future because further miniaturization and improvement of resolving power can be expected, as the integration technology makes progress.
As the solid state image sensing element, the charge coupled device (CCD) having two functions of photoelectric conversion and scanning is widely used. This CCD is roughly divided into a frame transfer type, a line transfer type and a vertical inter-line type.
In the frame transfer type CCD, firstly photoelectric conversion and signal accumulation are made at a light sensing part during a field period and the charges are put in parallel and transferred to and accumulated in an accumulating part during the short time of a vertical blanking period, and the shielded charges in the accumulating part equivalent to 1 scanning line are transferred in the standard scanning method by means of the horizontal register during the horizontal blanking period, and the signals are sequentially read out.
The line transfer type CCD is provided with a vertical output register and reads out the signals by switching the transferred signals per line.
In the vertical inter-line transfer type CCD, the light sensing part and transferring part are paired and arranged in a line in the longitudinal direction.
The line transfer type CCD can be made smaller than other types of CCD, but it has a disadvantage that when charges are transferred for signal reading, the incident light is received and the signal charge corresponding to a different picture element is superimposed and the smear phenomenon (picture becomes indistinct) occurs.